My friends made such a machanism. If the button is pressed, there is a possibility(not 100%) that the piston that is on the other sticky piston will be duplicated. We can also place any block on this piston. The machanism is also able to duplicate that block(not 100% possibility).
Attachment 2013-02-01_10.19.15.png is front view. The other one is back view.
This machanism works well in both 13w04a and 13w05a.